1. Field of the Invention
The present invention relates to a circuit for detecting a phase difference between two pulse signals having optional phases, and particularly to a pulse phase difference encoding circuit that can accurately detect the phase difference over a wide range.
2. Description of the Related Art
A prior art technique encodes a phase difference between two pulses PA and PB into a digital signal composed of a plurality of bits that represent a positive or negative shift (difference) between phases of the two pulses
and PB. The detection range of the phase shift of this technique can be expanded without deteriorating the detection accuracy by increasing the number of bits of the digital signal.
The increase in the number of bits, however, increases circuit scale. If the circuit scale must be kept as it is, the detection range is expandable only by sacrificing the detection accuracy.
When phases of two pulses PA and PB change in response to a change in a physical quantity, it is possible to find the change in the physical quantity by detecting a difference between the phases. Based on this idea, a sensor can be made. This sort of sensor must have a wide detection range and high detection accuracy to respond to sensing elements that cause large phase changes or have a variety of characteristics to cause a large phase difference. Further, for the sake of compactness and economy, the size of the sensor must not be increased excessively: